diff --git a/db/data/20251230000002_migrate_ax_modifiers_to_fk.rb b/db/data/20251230000002_migrate_ax_modifiers_to_fk.rb
new file mode 100644
index 0000000..d57266d
--- /dev/null
+++ b/db/data/20251230000002_migrate_ax_modifiers_to_fk.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+class MigrateAxModifiersToFk < ActiveRecord::Migration[8.0]
+  def up
+    # Build lookup cache: game_skill_id -> weapon_stat_modifier.id
+    modifier_lookup = WeaponStatModifier.pluck(:game_skill_id, :id).to_h
+
+    # Migrate CollectionWeapon ax_modifier1
+    CollectionWeapon.where.not(ax_modifier1: nil).find_each do |cw|
+      modifier_id = modifier_lookup[cw.ax_modifier1]
+      if modifier_id
+        cw.update_columns(ax_modifier1_ref_id: modifier_id)
+      else
+        Rails.logger.warn "[MigrateAxModifiers] Unknown ax_modifier1=#{cw.ax_modifier1} on CollectionWeapon##{cw.id}"
+      end
+    end
+
+    # Migrate CollectionWeapon ax_modifier2
+    CollectionWeapon.where.not(ax_modifier2: nil).find_each do |cw|
+      modifier_id = modifier_lookup[cw.ax_modifier2]
+      if modifier_id
+        cw.update_columns(ax_modifier2_ref_id: modifier_id)
+      else
+        Rails.logger.warn "[MigrateAxModifiers] Unknown ax_modifier2=#{cw.ax_modifier2} on CollectionWeapon##{cw.id}"
+      end
+    end
+
+    # Migrate GridWeapon ax_modifier1
+    GridWeapon.where.not(ax_modifier1: nil).find_each do |gw|
+      modifier_id = modifier_lookup[gw.ax_modifier1]
+      if modifier_id
+        gw.update_columns(ax_modifier1_ref_id: modifier_id)
+      else
+        Rails.logger.warn "[MigrateAxModifiers] Unknown ax_modifier1=#{gw.ax_modifier1} on GridWeapon##{gw.id}"
+      end
+    end
+
+    # Migrate GridWeapon ax_modifier2
+    GridWeapon.where.not(ax_modifier2: nil).find_each do |gw|
+      modifier_id = modifier_lookup[gw.ax_modifier2]
+      if modifier_id
+        gw.update_columns(ax_modifier2_ref_id: modifier_id)
+      else
+        Rails.logger.warn "[MigrateAxModifiers] Unknown ax_modifier2=#{gw.ax_modifier2} on GridWeapon##{gw.id}"
+      end
+    end
+  end
+
+  def down
+    # Reverse: copy FK back to integer columns
+    WeaponStatModifier.find_each do |modifier|
+      next unless modifier.game_skill_id
+
+      CollectionWeapon.where(ax_modifier1_ref_id: modifier.id)
+                      .update_all(ax_modifier1: modifier.game_skill_id)
+      CollectionWeapon.where(ax_modifier2_ref_id: modifier.id)
+                      .update_all(ax_modifier2: modifier.game_skill_id)
+      GridWeapon.where(ax_modifier1_ref_id: modifier.id)
+                .update_all(ax_modifier1: modifier.game_skill_id)
+      GridWeapon.where(ax_modifier2_ref_id: modifier.id)
+                .update_all(ax_modifier2: modifier.game_skill_id)
+    end
+  end
+end
diff --git a/db/migrate/20251230000002_add_weapon_stat_modifier_fks.rb b/db/migrate/20251230000002_add_weapon_stat_modifier_fks.rb
new file mode 100644
index 0000000..14fa62f
--- /dev/null
+++ b/db/migrate/20251230000002_add_weapon_stat_modifier_fks.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class AddWeaponStatModifierFks < ActiveRecord::Migration[8.0]
+  def change
+    # collection_weapons - add FK columns
+    add_reference :collection_weapons, :ax_modifier1_ref,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_reference :collection_weapons, :ax_modifier2_ref,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_reference :collection_weapons, :befoulment_modifier,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_column :collection_weapons, :befoulment_strength, :float
+    add_column :collection_weapons, :exorcism_level, :integer, default: 0
+
+    # grid_weapons - same pattern
+    add_reference :grid_weapons, :ax_modifier1_ref,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_reference :grid_weapons, :ax_modifier2_ref,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_reference :grid_weapons, :befoulment_modifier,
+                  foreign_key: { to_table: :weapon_stat_modifiers }
+    add_column :grid_weapons, :befoulment_strength, :float
+    add_column :grid_weapons, :exorcism_level, :integer, default: 0
+  end
+end
diff --git a/db/migrate/20251230000003_finalize_ax_modifier_columns.rb b/db/migrate/20251230000003_finalize_ax_modifier_columns.rb
new file mode 100644
index 0000000..6629249
--- /dev/null
+++ b/db/migrate/20251230000003_finalize_ax_modifier_columns.rb
@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class FinalizeAxModifierColumns < ActiveRecord::Migration[8.0]
+  def change
+    # Remove old integer columns
+    remove_column :collection_weapons, :ax_modifier1, :integer
+    remove_column :collection_weapons, :ax_modifier2, :integer
+    remove_column :grid_weapons, :ax_modifier1, :integer
+    remove_column :grid_weapons, :ax_modifier2, :integer
+
+    # Rename new FK columns to the original names
+    rename_column :collection_weapons, :ax_modifier1_ref_id, :ax_modifier1_id
+    rename_column :collection_weapons, :ax_modifier2_ref_id, :ax_modifier2_id
+    rename_column :grid_weapons, :ax_modifier1_ref_id, :ax_modifier1_id
+    rename_column :grid_weapons, :ax_modifier2_ref_id, :ax_modifier2_id
+  end
+end
diff --git a/db/migrate/20251230000004_add_augment_type_to_weapon_series.rb b/db/migrate/20251230000004_add_augment_type_to_weapon_series.rb
new file mode 100644
index 0000000..2714b5b
--- /dev/null
+++ b/db/migrate/20251230000004_add_augment_type_to_weapon_series.rb
@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class AddAugmentTypeToWeaponSeries < ActiveRecord::Migration[8.0]
+  def up
+    add_column :weapon_series, :augment_type, :integer, default: 0, null: false
+
+    # Migrate existing has_ax_skills: true to augment_type: 1 (ax)
+    execute <<-SQL.squish
+      UPDATE weapon_series
+      SET augment_type = 1
+      WHERE has_ax_skills = true
+    SQL
+
+    remove_column :weapon_series, :has_ax_skills
+  end
+
+  def down
+    add_column :weapon_series, :has_ax_skills, :boolean, default: false, null: false
+
+    # Migrate augment_type: 1 (ax) back to has_ax_skills: true
+    execute <<-SQL.squish
+      UPDATE weapon_series
+      SET has_ax_skills = true
+      WHERE augment_type = 1
+    SQL
+
+    remove_column :weapon_series, :augment_type
+  end
+end